A court in Siberia has ordered two defendants on trial over a deadly 2009 dam disaster to be held behind bars.

The court ruled that the former director of the Sayano-Shushenskaya hydroelectric power plant, Nikolai Nevolko, and its former deputy chief engineer, Yevgeny Shervarli, must be incarcerated for six months because they violated travel restrictrions.

Seventy-five people were killed when the Russia's largest hydroelectric power plant was flooded and badly damaged in an accident on August 17, 2009.

Nevolko, Shervarli and five other former senior managers of the facility have been charged with negligence and violation of safety regulations in the disaster, which highlighted problems with Russian indutrial facilities and infrastructure.

The court said they had violated travel restrictions by leaving the town of Sayanogorsk.